Multimedia Broadcast Multicast Services (MBMS) is a point-to-multipoint interface specification for cellular communication networks. MBMS is designed to provide efficient delivery of broadcast and multicast services within a particular geographical area. For broadcast transmission across multiple cells, MBMS defines transmission via single-frequency network configurations. Some potential applications for MBMS may include mobile television, radio broadcasting, and emergency alerts. As specified in 3GPP TS 36.331, “Radio Resource Control”, v. 12.1.0, when the MBMS service is enabled, some of the available subframes within the radio frames are periodically allocated to MBMS. The periodicity can be set to one, two, four, eight, sixteen, or thirty two radio frames. Normally, MBMS subframe allocation is semi-statically configured. The MBMS subframe pattern is indicated in a System Information Block 2 (SIB2) broadcast message as part of the MBMS Single Frequency Network (MBSFN)-Subframe Configuration Information Element (IE). User Equipment devices (UEs) that are not interested in the multicast service skip the MBMS subframes by just reading the Physical Downlink Common Control Channel (PDCCH) for any uplink grants.
MBMS subframes can be configured based on the expected MBMS service load. These MBMS subframes can be configured across a decided MBMS allocation period in any order or pattern. In this regard, FIG. 1 shows an example MBMS subframe allocation following a Distributed Assignment and a Dense Assignment. In a Distributed Assignment, the subframes are allocated across many frames. In a Dense Assignment, many of the subframes are allocated in one frame with less allocated in other frames.
If the cellular communication network also implements Voice over Internet Protocol (VoIP) (e.g., Voice over Long Term Evolution (VoLTE)), the VoIP Radio Access Bearers (RABs) typically transmit and receive packets every 20 milliseconds (ms) during a talk spurt. In other implementations, the VoIP RABs transmit every 40 ms during the talk spurt when two packets are bundled together. To conserve the battery power of the UE, VoIP users may operate with Discontinuous Reception (DRX) enabled. Typically the DRX period is set to the same periodicity as the VoIP RAB with the DRX ON TIME set to a minimum number of subframes to receive the VoIP packets. These DRX settings allow a UE to receive the VoIP RAB transmissions while conserving power by not receiving during other times.
When some of the subframes are already allocated for MBMS service, VoIP RABs cannot be received during those subframes. If these MBMS scheduled subframes interfere with the scheduled VoIP packet receptions, this may result in the VoIP UEs experiencing degradation in quality due to missed packets. These MBMS allocated subframes may also result in additional battery drain at the UE if the UE must maintain a longer DRX ON TIME in order to receive the VoIP RAB reception. As such, there is a need for improved MBMS scheduling and DRX parameter selection.